Paper feeding apparatus

ABSTRACT

A paper feeding apparatus includes a housing accommodating a plurality of papers, a pickup unit feeding the papers one by one, a movable plate provided in the housing, a friction member provided on the movable plate and on which lower ends of the papers accommodated in the housing abut, and an urging member urging the movable plate in a direction opposite from a paper feeding direction.

BACKGROUND OF THE INVENTION

The present invention relates to a paper feeding apparatus for a printer.

Currently, various paper feeding apparatuses for printers have been used. In particular, there has been used an apparatus having such a configuration as to obliquely hold and feed a paper. In the related paper feeding apparatus of this type, generally, a fixed friction pad on which the lower end of an accommodated paper bundle abuts is provided in the lower part of a back cover for obliquely holding a paper. A feeding paper is reliably separated from a next feeding paper by using the friction of the friction pad with the lower end of the paper which is fed out.

However, there are many kinds of papers to be used, for example papers having high and low rigidities. The fixed friction pad cannot necessarily accommodate all kinds of papers.

Therefore, there has been proposed a paper feeding apparatus in which surfaces having different coefficients of friction abut on the lower end of a paper depending on a difference in the rigidity of the paper (for example, see FIG. 10 of JP-A-11-11719).

The paper feeding apparatus has a slot provided on an abutment surface for the edge of a paper, the slot is provided with a projection. The surface of the projection is set to have a high coefficient of friction, and the abutment surface is set to have a low coefficient of friction. The paper abuts on the surface having the high or low coefficient of friction depending on the rigidity of the paper. With such structure, for example, a paper having a low rigidity (a plain paper) abuts on the surface of the projection having the high coefficient of friction and a paper having a high rigidity (a postcard) presses down the projection and abuts on the abutment surface having the low coefficient of friction. Accordingly, the papers having the low and high rigidities can easily be fed out by a roller.

In the paper feeding apparatus described in JP-A-11-11719, the projection is simply displaced vertically and the separating property of the paper depends on the maintenance of the two surfaces having different coefficients of friction. More specifically, a separating performance obtained by utilizing a friction is determined by only a difference between the coefficients of friction of the two surfaces. For this reason, it is hard to accommodate paper having different rigidities.

SUMMARY OF THE INVENTION

In consideration of the circumstances, it is an object of the invention to provide a paper feeding apparatus having a high reliability which can exhibit an excellent separating performance irrespective of the rigidity of a paper.

The object of the invention can be achieved by the following structures.

(1) A paper feeding apparatus, comprising:

-   -   a housing accommodating a plurality of papers;     -   a pickup unit feeding the papers one by one;     -   a movable plate provided in the housing;     -   a friction member provided on the movable plate and on which         lower ends of the papers accommodated in the housing abut; and     -   an urging member urging the movable plate in a direction         opposite from a paper feeding direction.

(2) The paper feeding apparatus according to (1), wherein the movable plate is pressed and tilted by the paper which is fed out by the pickup unit.

(3) The paper feeding apparatus according to (1) or (2), wherein the housing has an opening which is disposed on an extension of a paper feeding path toward a paper supply destination, and which allows feeding of the paper through an underside of the movable plate.

(4) The paper feeding apparatus according to (1), wherein the friction member is provided below the pickup roller.

(5). A paper feeding apparatus comprising:

-   -   a housing including a back cover and a bottom plate supporting a         plurality of papers, the housing having a paper outlet; and     -   a pickup unit selectively engageable with the of papers, the         pickup unit feeding the papers one by one from the housing to         the paper outlet,     -   wherein the bottom plate is pivotable between a full supporting         position and a partial supporting position by a force of a paper         being fed by the pickup unit, a pivot amount from the full         supporting position to the partial supporting position being         dependent on a strength of the paper being fed.

(6). The paper feeding apparatus according to (5), wherein the bottom plate comprises a friction member on which lower ends of the papers in the housing abut.

(7). The paper feeding apparatus according to (5), further comprising an urging member urging the bottom plate toward the full supporting position.

(8). A printer comprising a paper inlet for receiving papers for printing, and the paper feeding apparatus of (5).

(9). A method of feeding papers one by one to a paper outlet of a housing, the housing including a back cover and a bottom plate, the method comprising:

-   -   supporting a plurality of papers in the housing;     -   selectively engaging a pickup unit with the papers;     -   feeding the papers one by one from the housing to the paper         outlet; and     -   pivoting the bottom plate between a full supporting position and         a partial supporting position by a force of a paper being fed by         the pickup unit, wherein a pivot amount from the full supporting         position to the partial supporting position is dependent on a         strength of the paper being fed.

(10). The method according to (9), further comprising urging the bottom plate toward the full supporting position.

(11). The method according to (9), wherein the supporting step comprises abutting the papers on a friction member disposed on the bottom plate.

The paper feeding apparatus according to the invention includes a housing having a back cover for accommodating a paper bundle in an oblique erecting posture, the pickup roller for pressing a paper in an uppermost portion of the paper bundle and feeding out the paper in the uppermost portion by its own rotation while moving downward, and the movable plate having a friction member provided under the back cover and serving to separate the paper thus fed out by an abutment of a lower end of the paper bundle accommodated in the back cover. The movable plate is rotatably supported by a shaft provided on the back cover side so that a portion extended in a paper feeding direction can be tilted in a vertical direction and is urged upward by the urging member. Accordingly, the movable plate is tilted depending on the rigidity of the paper which is fed out, and the paper can be separated depending on a frictional force between the friction member and the tip of the paper.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein:

FIG. 1 is a perspective view showing the appearance of a paper feeding apparatus according to an embodiment of the invention;

FIG. 2 is a sectional side view showing a state in which the paper feeding apparatus of FIG. 1 is attached to a printer body portion 1;

FIG. 3 is a perspective view showing the paper feeding apparatus according to the embodiment as seen from a back side;

FIG. 4 is a view showing the paper feeding apparatus according to the embodiment seen from an oblique back side, a portion provided with a pickup unit being cut away;

FIG. 5 is a view showing only the portion provided with the pickup unit in the paper feeding apparatus according to the embodiment as seen from an oblique back side, a back cover being taken away;

FIG. 6 is a side view schematically showing the relationship between the pickup unit and a friction pad;

FIG. 7 is a perspective view showing only the pickup unit;

FIG. 8 is a side view showing the pickup unit;

FIG. 9 is an explanatory view showing a torque transmitting member (a clutch spring 60) attached to the driving shaft of the pickup unit;

FIGS. 10A and 10B are views showing the relationship between a pickup roller in the pickup unit illustrated in FIG. 6 and the paper guide surface of a back cover, FIG. 10A being a sectional side view and FIG. 10B being a plan view showing the paper guide surface;

FIG. 11 is an enlarged perspective view showing a main part, illustrating the relationship between the pickup roller in the pickup unit of FIG. 6 and the paper guide surface of the back cover;

FIG. 12 is a partial perspective view showing the inner part of the paper feeding apparatus;

FIGS. 13A to 13C are explanatory views showing the proper attachment angle of a cleaning member in the paper feeding apparatus, FIG. 13A being a view showing a non-preferable attachment angle, and FIGS. 13B and 13C being views showing preferable attachment angles;

FIG. 14 is an explanatory view showing the action of the friction pad in the paper feeding apparatus;

FIG. 15 is an explanatory view showing an action for feeding out paper having a high rigidity in the paper feeding apparatus;

FIG. 16 is an explanatory view showing an action for feeding out paper having a low rigidity in the paper feeding apparatus; and

FIG. 17 is an explanatory view showing the case that the rear end of a paper in the paper feeding apparatus is caused to escape rearward.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A paper feeding apparatus according to a embodiment of the invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view showing the appearance of the paper feeding apparatus according to the embodiment which is to be attached to a printer body portion, FIG. 2 is a sectional side view showing a state in which the paper feeding apparatus illustrated in FIG. 1 is attached to the printer body portion, and FIG. 3 is a perspective view showing the paper feeding apparatus illustrated in FIG. 1 as seen from a back side.

A paper feeding apparatus 10 according to the embodiment is an ASF (automatic sheet feeder) capable of accommodating a plurality of papers (cut-form papers) having a predetermined size and feeding the papers one by one into a printer body portion 1.

The paper feeding apparatus 10 is mainly constituted by a housing 13 including a lower case 11 and an upper cover 12. The lower case 11 is a box member formed integrally by a resin which has a front cover 14, a back cover 15 constituting a paper guide wall, right and left side covers 16 and 17, and a bottom cover 18. As shown in FIG. 2, paper S is superposed on a paper guide surface 15 a of the back cover 15 in an oblique erecting posture, and is thus accommodated and held.

An upper opening 20 constituted by the front cover 14, the side covers 16 and 17, and the back cover 15 is provided on the upper surface side of the lower case 11. The upper cover 12 is inserted from the upper opening 20 and is fitted in the lower case 11 in order to block a part of the upper opening 20. A portion which is not blocked with the upper opening 20 is constituted as a paper inserting port through which paper S is inserted obliquely.

The side covers 16 and 17 are provided with hook portions 9 for attaching the paper feeding apparatus 10 to the printer body portion 1. The hook portions 9 are inverse L-shaped, are protruded toward the opposite side of the back cover 15 and are bulged downward, for example, and are caught on engagement holes (not shown) in the back face portion of the printer body portion 1 so that the paper feeding apparatus 10 is detachably fixed to the printer body portion 1.

A plane-shaped paper guide 19 for supporting paper in a portion positioned above the back cover 15, and a paper guide member 21 for inserting and guiding the paper S inserted through the upper opening 20 are provided on the upper end of the back cover 15.

The paper guide member 21 is constituted slidably along the upper end of the back cover 15. A width between the paper guide member 21 and the side cover 17 is set almost equal to the width of the paper S to be inserted so that both ends of the paper S are guided by the side cover 17 and the paper guide member 21 so that the paper S can be inserted without inclination in a transverse direction.

As shown in FIG. 2, a movable plate 30 having an upper surface against which the lower end of the paper S is pressed is provided at the inside of the lower part of the back cover 15 of the lower case 11. The movable plate 30 is rotatably provided so as to vary an inclination angle with respect to the back cover 15. The movable plate 30 will be described later in detail.

A lower opening 22 constituted by the front cover 14, the side covers 16 and 17, and the bottom cover 18 is provided on the bottom face side of the lower case 11. The lower opening 22 constitutes a paper discharge port for discharging the paper S inserted from the upper opening 20 and defines a paper inserting port toward a paper feeding path 5 of the printer body portion 1. As shown in FIG. 3, moreover, a slit-shaped opening 23 for manually inserting the paper S and discharging the rear end of the paper S outside of the apparatus in the beginning of the feed of the paper S is provided on the lower end of the back cover 15.

An attachment rib 12 a formed integrally with the upper cover 12 is provided on the inside of the upper cover 12 (the back cover 15 side). The attachment rib 12 a has a guide end 12 b provided in the direction of insertion of the paper S. The guide end 12 b of the attachment rib 12 a positions the paper S inserted from the upper opening 20 together with the back cover 15, and guides the paper S to be discharged from the opening 22 as the paper discharge port. A pickup unit 50 for paper feeding is fixed to the attachment rib 12 a.

FIG. 4 is a view seen from an oblique back side, showing a portion provided with the pickup unit 50 which is cut away. FIG. 4 shows a state in which the pickup unit 50 is placed in a standby position. Moreover, FIG. 5 is a view seen from an oblique back side, showing the back cover 15 which is cut away in only the portion provided with the pickup unit 50. FIG. 5 shows the pickup unit 50 which is floated from the standby position. FIG. 6 is a sectional view conceptionally showing the positional relationship between the pickup unit 50 and movable plate 30 and the other members, FIG. 7 is a perspective view showing the pickup unit 50, FIG. 8 is a side view showing the pickup unit 50, and FIG. 9 is an explanatory view showing a clutch spring 60 (a torque transmitting member) attached to the driving shaft of the pickup unit 50.

As shown in FIG. 6, 7 or 8, the pickup unit 50 includes a pickup lever 51, a driving shaft 52 to be driven by a motor 49 (which is shown in only FIG. 8), a pickup roller 53 for feeding the paper S toward the printer body portion 1 by pressing its peripheral surface against the paper S, and gears (rotation transmitting members) 54 to 59 which transmit a rotation driving force between the driving shaft 52 and the pickup roller 53 and are sequentially engaged. The gear 54 at an input stage is integrated with the driving shaft 52 and the gear 59 at an output stage is integrated with the pickup roller 53.

The pickup roller 53 has a rolling contact surface 53 b formed by wrapping a high friction material such as rubber lining around the outer periphery of a core member such as a plastic. Low friction rotating members 53 a having a diameter smaller than the diameter of the rolling contact surface 53 b are provided on both end sides of the pickup roller 53 in the axial direction of the pickup roller 53.

The low friction rotating member 53 a according to the embodiment is formed by leaving the peripheral surface of the core member without wrapping the high friction material. The low friction rotating member 53 a has a surface which is more slidable than the rolling contact surface 53 b. The low friction rotating member 53 a can abut, with slipping, on the back cover 15 provided around a relief hole 15 b which will be described below, and constitutes an engaging mechanism which will be described below.

As shown in FIG. 4, the pickup lever 51 has an upper end side (a base end side) supported rotatably on the attachment rib 12 a of the upper cover 12 constituting the housing 13. The pickup lever 51 is rotated toward the paper bundle side, thereby causing the pickup roller 53 provided rotatably on the lower end (tip side) of the pickup lever 51 to be pressed against the top paper S of the paper bundle having a plurality of papers S. By rotating the pickup roller 53 in a state that the rolling contact surface 53 b of the pickup roller 53 is pressed against the paper S, it is possible to feed out the paper S one by one.

As shown in FIGS. 6 and 7, the driving shaft 52 is provided along a rotating support axis P1 of the pickup lever 51. A clutch spring 60 serving as the torque transmitting member is provided between the driving shaft 52 and the pickup lever 51.

The clutch spring 60 is a friction clutch for integrally rotating the driving shaft 52 and the pickup lever 51 by frictional engagement. The clutch spring 60 serves to transmit a torque from the driving shaft 52 to the pickup lever 51 until a predetermined torque or more acts on the driving shaft 52 and to permit the relative rotation of the driving shaft 52 to the pickup lever 51 when the predetermined torque or more acts on the driving shaft 52.

As shown in FIGS. 7 to 9, the clutch spring 60 has a spiral spring drum portion 60 a formed by a torsion coil spring to be frictionally engaged with the outer periphery of the driving shaft 52, and has two hooks 61 which are continuously linked to the spring drum portion 60 a and can be engaged with hook receiving portions 51 p formed on the pickup lever 51 respectively. The permitted transmitting torque of a torque transmitting member (a friction clutch) is set by the clutch spring 60 by a frictional engaging force between the spring drum portion 60 a and the driving shaft 52.

The operation of the clutch spring 60 will be specifically described. When the driving shaft 52 of the pickup unit 50 is driven by the motor 49, the clutch spring 60 engaged frictionally with the outer periphery of the driving shaft 52 is rotated integrally with the driving shaft 52 and one of the hooks 61 abuts on one of the hook receiving portions 51 p. When the driving shaft 52 is further rotated with one of the hooks 61 abutting on the hook receiving portion 51 p, the abutting hook 61 of the clutch spring 60 rotated together with the driving shaft 52 presses the hook receiving portion 51 p in the circumferential direction of the driving shaft 52 so that the driving shaft 52 and the pickup lever 51 are interlockingly rotated integrally through the clutch spring 60.

For example, in the case where the pickup lever 51 is rotated in the direction of the paper, the pickup lever 51 is moved to a position in which the pickup roller 53 provided on the tip of the pickup lever 51 abuts on the paper S as shown in FIG. 6. When the motor 49 is further driven with the pickup roller 53 abutting on the paper S, a torque which is equal to or greater than a maximum static friction torque between the driving shaft 52 and the clutch spring 60 acts by a reaction received from the paper S by the pickup lever 51, and the outer periphery of the driving shaft 52 is disengaged from the clutch spring 60, that is, the interlock of the driving shaft 52 and the clutch spring 60 is released so that the driving shaft 52 is rotated with respect to the pickup lever 51. Consequently, the rotation of the driving shaft 52 is transmitted to the pickup roller 53 through the gears (rotation transmitting members) 54 to 59 so that the pickup roller 53 is rotated.

In order to conform the direction of the rotation of the driving shaft 52 for feeding the paper by the pickup roller 53, the number of the intermediate gears 55 to 58 interposed between the gear 54 at the input stage and the gear 59 at the output stage is set to be even.

As shown in FIGS. 3 and 4, the relief hole 15 b for avoiding an interference with the rolling contact surface (rubber lining surface) 53 b of the pickup roller 53 is provided in the opposed portion to the pickup roller 53 in the back cover 15. The relief hole 15 b is provided to prevent the pickup roller 53 from locking by the frictional force generated by the direct contact of the rolling contact surface 53 b of the pickup roller 53 with the paper guide surface 15 a when all of the paper S is gone from the paper guide surface 15 a of the back cover 15.

The relief hole 15 b is set to be slightly larger than a width in the axial direction of the rolling contact surface 53 b. As shown in FIG. 10A, moreover, the rocking position of the pickup lever 51 is controlled in such a manner that the pickup roller 53 does not come in contact with the back cover 15 with the rolling contact surface 53 b of the pickup roller 53 inserting into the relief hole 15 b to some extent as shown in FIG. 10A. For this reason, an engaging mechanism is provided between the pickup lever 51 and the housing 13. The engaging mechanism serves to control the rocking position of the pickup roller 53, thereby preventing contact with the back cover 15 when the rolling contact surface 53 b enters the relief hole 15 b.

As shown in FIGS. 10 and 11, the engaging mechanism according to the embodiment includes the low friction rotating members 53 a provided on both end sides in the axial direction of the pickup roller 53, and a receiving portion 15 g on which the low friction rotating member 53 a abuts in the paper guide surface 15 a provided around the relief hole 15 b.

The low friction rotating member 53 a is a portion of the core member remaining without the rubber lining as described above. The low friction rotating member 53 a has a smaller frictional resistance than that of the rolling contact surface 53 b and can smoothly carry out slipping even if it comes in contact with the receiving portion 15 g provided on the paper guide surface 15 a. Thus, a high frictional force can be prevented from being generated.

In FIG. 10B, a portion shown in cross-hatching indicates a cross section of the opening surface of the pickup roller 53 and the relief hole 15 b (an opening surface on the paper guide surface 15 a side) which is obtained when the rolling contact surface 53 b of the pickup roller 53 enters the relief hole 15 b.

It is sufficient that the relief hole 15 b is sized to avoid contact with the rolling contact surface 53 b of the pickup roller 53 as the rocking position is controlled by the engaging mechanism, and a depth and a sectional shape are not restricted but are preferably as small as possible in order for the back cover 15 to sufficiently fulfill the paper guide function.

As shown in FIGS. 10A, 10B and 11, furthermore, a paper holding friction member 15 c such as a cork sheet which has a higher frictional resistance than that of the paper guide surface 15 a and has a lower frictional resistance than that of the rolling contact surface 53 b, is provided on the paper guide surface 15 a disposed around the relief hole 15 b.

Even if the pressing force of the pickup roller 53 against the paper S is reduced when the second to last paper S is fed, and the frictional force between the paper guide surface 15 a and the last paper S is reduced, the last paper S is still held by the paper holding friction member 15 c. Therefore, feeding of two sheets simultaneously is prevented.

The paper holding friction member 15 c is formed into a U-shape excluding a side portion in a paper feeding direction in four sides surrounding the relief hole 15 b. The reason is that there is a possibility that a frictional resistance in that portion might get in the way, and the last paper S would not be fed smoothly if the paper holding friction member 15 c is provided in the side portion in the paper feeding direction (downward in FIG. 10B). The receiving portion 15 g against which the low friction rotating member 53 a of the pickup roller 53 hits is provided inside of the paper holding friction member 15 c.

As shown in FIG. 6, a cleaning member 40 formed by a high friction material for cleaning the rolling contact surface 53 b of the pickup roller 53 by the rotation of the pickup roller 53 is positioned such that the peripheral surface of the pickup roller 53 is pressed against the cleaning member 40 when the pickup unit 50 is rotated away from the paper bundle S to a standby position.

As shown in FIGS. 6 and 12, the movable plate 30 is provided under the back cover 15. The lower end of the paper bundle accommodated and held in the back cover 15 abuts on the movable plate 30. The movable plate 30 separates the paper S which is fed out and is rotatably supported by a shaft 31 provided on the back cover 15 side. Consequently, an extended portion 30 a extended in the paper feeding direction can be tilted in a vertical direction. The extended portion 30 a of the movable plate 30 is urged by a spring 32 so as to be lifted upward.

A friction member 33 constituted by a resin having a high coefficient of friction is attached to a partial region in the longitudinal direction of the movable plate 30 on an upper surface 30 b of the movable plate 30. The friction member 33 is a paper holding member for holding the paper by a higher frictional force than the frictional force of other regions on the upper surface 30 b of the movable plate 30 to which the friction member 33 is not attached. The paper bundle S has a tip engaged with the friction member 33 and is thus held on the upper surface 30 b of the movable plate 30.

In the embodiment, it is necessary to provide the friction member 33 and the relief hole 15 b on the inside of the movable range of the paper guide member 21. It is preferable that the friction member 33 should be positioned obliquely under the relief hole 15 b, that is, under the pickup roller 53.

Next, description will be given to the action of the paper feeding apparatus 10 according to the embodiment.

In the embodiment, the driving shaft 52 is rotated by the motor 49, and the pickup lever 51 can be thus rotated through the clutch spring 60 as the torque transmitting member until a predetermined torque or more acts on the driving shaft 52. In that case, the direction of the rotation of the driving shaft 52 for feeding the paper by the pickup roller 53 is identical to the rotation direction of the driving shaft 52 in the rotation of the pickup lever 51 toward the paper S through the clutch spring 60. When the driving shaft 52 is rotated in the paper feeding direction, accordingly, the pickup roller 53 is pressed against the paper bundle. When the pickup roller 53 is pressed against the paper bundle, a torque acting on the driving shaft 52 is equal to or greater than a set torque. Consequently, the driving shaft 52 is rotated with respect to the pickup lever 51. The pickup roller 53 is rotated by the rotation of the driving shaft 52 and feeds one of the pressed papers S toward the printer body portion 1.

In this case, the pressing force of the pickup roller 53 is automatically determined by the set torque of the clutch spring 60 as the torque transmitting member. Accordingly, the pickup roller 53 can be pressed against the bundle of the papers S by a constant pressing force irrespective of the thickness of the bundle of the papers S (the number of the papers).

When the pickup unit 50 is returned to the standby position after the paper is completely fed, the motor 49 is rotated in reverse so that the driving shaft 52 is rotated in an opposite direction. When the driving shaft 52 is rotated in the opposite direction, the pickup lever 51 and the pickup roller 53 are automatically rotated away from the bundle of the papers S. The pickup roller 53 can easily pickup the paper S out of the paper feeding apparatus 10 without holding the bundle of the papers S.

With the spiral clutch spring 60 used as the torque transmitting member, it is possible to obtain an advantage that the driving shaft 52 and the pickup lever 51 can be engaged with and disengaged from each other by using small and inexpensive components and the components can easily be arranged. The pressing force of the pick-up roller 53 is automatically determined by the frictional engaging torque of the clutch spring 60.

Next, description will be given to the operation of the movable plate 30.

When the pickup roller 53 applies a force as to move the paper S downward by when the paper is fed, the lower end of the paper S first presses the upper surface 30 b of the movable plate 30, particularly, the friction member 33 provided on the upper surface 30 b. When the friction member 33 of the movable plate 30 is pressed, the movable plate 30 is tilted downward against the urging force of the spring 32. In other words, the pickup roller 53 feeds out the paper S so that the paper S presses the upper surface 30 b of the movable plate 30, particularly, the friction member 33. Consequently, the movable plate 30 is tilted. A force for holding the paper S depends on the coefficient of friction of the friction member 33 provided on the upper surface 30 b of the movable plate 30, the strength (rigidity) of the paper S and the angle of the movable plate 30.

When the movable plate 30 is gradually tilted, a force for disengaging the paper S from the friction member 33 and feeding out the paper S becomes greater than the holding force for holding the paper S in the friction member 33. The force for holding the paper S by the friction member 33 is gradually reduced. The moment that a certain angle at which the force for feeding out the paper S becomes greater than the force for holding the paper S is reached, the paper S is disengaged from the friction member 33 so that the paper S is fed toward the printer body portion 1.

When paper having a low rigidity (a paper having a small strength: a plain paper) S1 is fed as shown in FIGS. 14 and 15, the paper itself is apt to be flexed. Accordingly, the movable plate 30 is not greatly tilted but the paper S1 is flexed so that an angle between the paper S1 and the friction member 33 is decreased, and the force for holding the paper S1 is reduced. Accordingly, a friction angle with the lower end of the paper S1 fed through the movable plate 30 (the angle of the movable plate 30) has a suitable value without applying a great load to the paper S1 so that the paper S1 can smoothly be separated and fed out.

Even when in the case that the angle of the movable plate 30 is small, the paper S1 is guided to the opening 22 along the guide end 12 b of the attachment rib 12 a formed integrally with the upper cover 12 and is delivered from the opening 22 to the paper feeding path 5 of the printer body portion 1. More specifically, when the paper S1 has a small strength and the paper separated from the movable plate 30 is not exactly fed toward the opening 22, the paper S1 is guided toward the opening 22 along the guide end 12 b and is reliably delivered to the paper feeding path 5 of the printer body portion 1.

On the other hand, when a paper having a high rigidity (a paper having a great strength: a postcard) S2 is to be fed out as shown in FIGS. 14 and 16, the paper itself requires greater force to flex. If the movable plate 30 is not greatly tilted, accordingly, an angle between the paper S2 and the friction member 33 is not reduced. Therefore, the movable plate 30 is tilted farther downward in a state that a greater load is applied to the paper S2 having a high rigidity as compared with the paper S1. When the movable plate 30 is gradually tilted, the angle of the movable plate 30 with respect to the paper bundle including the paper S2 is decreased so that the friction angle with respect to the lower end of the paper S2 to be fed out has a suitable value. Consequently, the paper S2 can be smoothly separated and fed out.

In other words, in the paper feeding apparatus 10 according to the embodiment, the movable plate 30 is tilted so that the paper can be smoothly separated and supplied without the influence of the rigidity (strength) of each of the papers S1 and S2. Accordingly, the movable plate 30 separates each of the papers S at a suitable friction angle for the rigidity of the paper S. For example, it is possible to reliably separate the paper S irrespective of a rigidity, e.g., obtained by a difference in the thickness of the paper S.

If the friction member 33 is provided obliquely under the relief hole 15 b, that is, under the pickup roller 53, the friction member 33 is disposed in the paper feeding direction based on the pickup roller 53. Accordingly, the friction member 33 can receive a force for feeding out the paper S by the rotating force of the pickup roller 53 almost perpendicularly to the paper feeding direction, and a friction force between the tip of the paper S and the friction member 33 can be efficiently gained without torsion or flexure of the paper in the transverse direction thereof. Moreover, the paper resists being distorted or flexed in the transverse direction of the paper. Consequently, the paper can easily be delivered within an assumed range, and precision in a paper delivery position can easily be obtained.

After the paper is completely fed, the driving shaft 52 is rotated in a reverse direction and the pickup lever 51 is rotated so that the pickup roller 53 is separated from the paper bundle. Therefore, it is possible to easily take the paper or the paper bundle out of the paper feeding apparatus 10. When the driving shaft 52 is continuously rotated for several seconds such that the pickup lever 51 is rotated to a standby position, the peripheral surface of the pickup roller 53 is rubbed against the cleaning member 40 and refuse on the paper and various components coating the paper which attached to the peripheral surface of the pickup roller 53 are shaved off by the cleaning member 40 so that the peripheral surface of the pickup roller 53 can be cleaned. The pressing force for the cleaning member 40 is determined by the set torque of the clutch spring 60.

In the paper feeding apparatus 10 according to the embodiment, it is thus possible to automatically clean the pickup roller 53 by simply returning the pickup unit 50 to the standby position. Consequently, it is possible to enhance the durability of the pickup roller 53 and to prevent a paper feeding failure by maintaining a stable coefficient of friction.

As shown in FIGS. 13A to 13C, it is preferable that the attachment angle of the cleaning member 40 should be set equal to the angle of a tangential line PS drawn from the rotating support axis P1 of the pickup lever 51 to the peripheral surface of the pickup roller 53 (a state shown in FIG. 13B) or the cleaning member 40 should be tilted in such that a closer portion to the rotating support axis P1. is placed on an inside from the tangential line PS (a state in FIG. 13C). The reason is that when the cleaning member 40 is tilted in such that the closer portion to the rotating support axis P1 is placed on the outside of the tangential line PS (a state in FIG. 13A), a friction force M applied by the rotation of the pickup roller 53 (a rotation in the direction of an arrow R1) acts as a force for locking the rotation of the pickup roller 53.

When the paper S is regulated by a forward or backward movement to take out a tip thereof, there is a possibility that the rear end of the paper S to be moved backward might interfere with the movable plate 30 when the strength of the paper S is great. In the paper feeding apparatus 10 according to the embodiment, however, the opening 23 is formed on the lower end of the back cover 15 as shown in FIG. 17. Therefore, the rear end of the paper S can be moved rearward from the opening 23 on the back face. Therefore, when the tip of the high strength paper S is to be taken out, the rear end of the paper S is smoothly moved. The opening 23 is positioned on the extended line of the paper feeding path of the printer body portion 1 as a paper supply source, and is placed in such a position that the paper S can be moved through the underside of the movable plate 30.

If the relief hole 15 b is not provided on the back cover 15, there is a possibility that the rolling contact surface 53 b of the pickup roller 53 might directly come in contact with the paper guide surface 15 a when the paper S is gone from the paper guide surface 15 a. In the paper feeding apparatus 10 according to the embodiment, however, the relief hole 15 b for avoiding the interference with the rolling contact surface 53 b is provided in the opposed position to the rolling contact surface 53 b of the pickup roller 53 in the back cover 15, and a contact with the paper guide surface 15 a is prevented by the engaging mechanism when the rolling contact surface 53 b enters the relief hole 15 b.

In the case that the paper S is gone from the paper guide surface 15 a, accordingly, the rolling contact surface 53 b of the pickup roller 53 enters the relief hole 15 b and does not directly hit against the paper guide surface 15 a. This state is maintained by the abutment of the low friction rotating member 53 a provided adjacently to both sides of the pickup roller 53 on the receiving portion 15 g provided on the paper guide surface 15 a to regulate a position. In addition, in this state, the low friction rotating member 53 a simply carries out the slipping smoothly with respect to the receiving portion 15 g and high friction is not generated. For this reason, an excessive load is not applied to the pickup roller 53 and the pickup lever 51.

Accordingly, the rolling contact surface 53 b of the pickup roller 53 can carry out slipping without coming in contact with another member (the back cover 15) and friction is rarely generated between the pickup roller 53 and the paper guide surface 15 a so that the pickup roller 53 can be prevented from being locked.

When the second to last paper S is fed, the last paper S is stably held by the paper holding friction member 15 c provided around the relief hole 15 b, and feeding of two sheets simultaneously is prevented.

Furthermore, the relief hole 15 b is provided on the back cover 15, and the paper holding friction member 15 c is simply provided therearound. As compared with the case in which a free rotating roller and a spring are provided as in a related paper feeding apparatus, the number of components and manufacturing costs are reduced.

In the paper feeding apparatus 10 according to the embodiment, moreover, when the paper S is gone and the rolling contact surface 53 b of the pickup roller 53 enters the relief hole 15 b, the position of the pickup roller 53 is regulated by the abutment of the low friction rotating member 53 a.

As a result, in the closest position to the rolling contact surface 53 b of the pickup roller 53 to prevent contact with the back cover 15, it is possible to reliably regulate the rocking position of the pickup roller 53.

Accordingly, it is possible to prevent a situation that the rolling contact surface 53 b of the pickup roller 53 hits against the paper guide surface 15 a by mistake due to an assembly error. Thus, it is possible to enhance paper feeding reliability.

While the clutch spring 60 is used as the torque transmitting member in the embodiment, it is not limited. It is sufficient that an engagement with the driving shaft 52 is carried out until a torque having a predetermined value or more is applied, and the engagement is released when the torque having the predetermined value or more is applied.

The engaging mechanism of the paper feeding apparatus 10 according to the invention is not limited to the structure according to the embodiment but it is apparent that the same engaging mechanism can employ various structures to prevent contact with the back cover 15 when the rolling contact surface 53 b of the pickup roller 53 enters the relief hole 15 b.

For example, it is also possible to provide a stopper to hit against the back cover 15 in the rocking tip portion of the pickup lever 51, thereby regulating the rocking range of the pickup roller 53. By engaging the base end side of the pickup lever 51 with a stopper protruded from the attachment rib 12 a of the upper cover 12, it is also possible to regulate the rocking range of the pickup roller 53.

It is preferable to precisely regulate the position of the pickup roller 53 in a close position to the back cover 15 if possible. When the low friction rotating member 53 a provided on both end sides in the axial direction of the pickup roller 53 is caused to abut on the receiving portion 15 g provided around the relief hole 15 b, it is not necessary to precisely configure the pickup lever 51 components to be rotated by the driving shaft 52. Consequently, it is possible to reduce manufacturing costs of the engaging mechanism.

While the paper feeding apparatus used in the printer is described in the embodiment, the paper feeding apparatus according to the present invention may be applied to a copy machine, a facsimile and a scanner and so on.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 

1. A paper feeding apparatus, comprising: a housing accommodating a plurality of papers; a pickup unit feeding the papers one by one; a movable plate provided in the housing; a friction member provided on the movable plate and on which lower ends of the papers accommodated in the housing abut; and an urging member urging the movable plate in a direction opposite from a paper feeding direction.
 2. The paper feeding apparatus according to claim 1, wherein the movable plate is pressed and tilted by the paper which is fed out by the pickup unit.
 3. The paper feeding apparatus according to claim 1, wherein the housing has an opening which is disposed on an extension of a paper feeding path toward a paper supply destination, and which allows feeding of the paper through an underside of the movable plate.
 4. The paper feeding apparatus according to claim 1, wherein the friction member is provided below the pickup roller.
 5. A paper feeding apparatus comprising: a housing including a back cover and a bottom plate supporting a plurality of papers, the housing having a paper outlet; and a pickup unit selectively engageable with the of papers, the pickup unit feeding the papers one by one from the housing to the paper outlet, wherein the bottom plate is pivotable between a full supporting position and a partial supporting position by a force of a paper being fed by the pickup unit, a pivot amount of the bottom plate from the full supporting position to the partial supporting position being dependent on a strength of the paper being fed.
 6. The paper feeding apparatus according to claim 5, wherein the bottom plate comprises a friction member on which lower ends of the papers in the housing abut.
 7. The paper feeding apparatus according to claim 5, further comprising an urging member urging the bottom plate toward the full supporting position.
 8. A printer comprising a paper inlet for receiving papers for printing, and the paper feeding apparatus of claim
 5. 9. A method of feeding papers one by one to a paper outlet of a housing, the housing including a back cover and a bottom plate, the method comprising: supporting a plurality of papers in the housing; selectively engaging a pickup unit with the papers; feeding the papers one by one from the housing to the paper outlet; and pivoting the bottom plate between a full supporting position and a partial supporting position by a force of a paper being fed by the pickup unit, wherein a pivot amount of the bottom plate from the full supporting position to the partial supporting position is dependent on a strength of the paper being fed.
 10. The method according to claim 9, further comprising urging the bottom plate toward the full supporting position.
 11. The method according to claim 9, wherein the supporting step comprises abutting the papers on a friction member disposed on the bottom plate. 